Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J35/00—X-ray tubes
  • H01J35/02—Details
  • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
  • H01J35/06—Cathodes
  • H01J35/064—Details of the emitter, e.g. material or structure
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J35/00—X-ray tubes
  • H01J35/02—Details
  • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
  • H01J35/06—Cathodes
  • H01J35/065—Field emission, photo emission or secondary emission cathodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J35/00—X-ray tubes
  • H01J35/02—Details
  • H01J35/16—Vessels; Containers; Shields associated therewith
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
  • H01J9/24—Manufacture or joining of vessels, leading-in conductors or bases
  • H01J9/26—Sealing together parts of vessels
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
  • H01J9/38—Exhausting, degassing, filling, or cleaning vessels
  • H01J9/385—Exhausting vessels
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2235/00—X-ray tubes
  • H01J2235/06—Cathode assembly
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J35/00—X-ray tubes

Definitions

• the present application is related generally to electron emitters in x-ray tubes.
• a critical component of x-ray tubes is the electron emitter, such as a filament for example.
• a solid support for the electron emitter can be important because motion of such support can cause the electron emitter to bend or distort. Bending or distortion of the electron emitter during use can result in early electron emitter failure, which can cause the x-ray tube to fail.
• the cost of the electron emitter support both material and manufacturing cost, can be important for a low x-ray tube cost. Precise and repeatable placement of the electron emitter in the x-ray tube during manufacturing can be important to ensure consistency of x-ray output between different units of a single x-ray tube model. Long x-ray tube life also can be important.
• the present invention is directed to various embodiments of x-ray tubes with electron emitter supports that satisfy these needs. Each embodiment may satisfy one, some, or all of these needs. The present invention is also directed to a method of evacuating and sealing an x-ray tube that satisfies one, some, or all of these needs.
• the x-ray tube comprises an evacuated, electrically-insulative enclosure with a cathode and an anode at opposite ends thereof.
• Dual, electrically- conductive emitter tubes can extend from the cathode towards the anode.
• the emitter tubes can comprise an inner tube and an outer tube with the inner tube disposed at least partially within the outer tube.
• the inner and outer tubes can have opposite ends comprising a near end associated with the cathode and a far end disposed closer to the anode. There can be a first gap between the far end of the outer tube and the anode and a second gap between the far end of the inner tube and the anode.
• An electron emitter can be coupled between the far end of the inner tube and the far end of the outer tube.
• the inner and outer tubes can be electrically isolated from one another except for the electron emitter.
• the method, of evacuating and sealing an x-ray tube can comprise some or all of the following steps:
• each of the inner and outer tubes having opposite ends comprising a near end associated with the cathode and a far end disposed closer to the anode;
• the inner and outer tubes being electrically isolated from one another except for the electron emitter;
• FIGs. 1-2 are schematic, longitudinal, cross-sectional side views of an x- ray tube including dual, electrically-conductive emitter tubes as an electron emitter support, in accordance with an embodiment of the present invention
• FIG. 3 is a schematic, lateral, cross-sectional side view of an x-ray tube including dual, electrically-conductive emitter tubes as an electron emitter support (this lateral side view is orthogonal to the longitudinal side views of FIGs. 1-2), in accordance with an embodiment of the present invention
• FIG. 4 is a schematic, longitudinal, cross-sectional side view of an x-ray source including an x-ray tube, similar to the x-ray tubes shown in FIGs. 1-3, and a power supply electrically connected to the x-ray tube, in accordance with an embodiment of the present invention
• FIG. 5 is a schematic, longitudinal, cross-sectional side view of an x-ray tube including an open inner tube, in accordance with an embodiment of the present invention
• FIG. 6 is a schematic, longitudinal, cross-sectional side view of an x-ray tube including a vacuum pump attached to the open inner tube and drawing a vacuum on an interior of the x-ray tube, in accordance with an embodiment of the present invention.
• FIG. 7 is a schematic, longitudinal, cross-sectional side view of an x-ray tube with the inner tube being pinched shut, in accordance with an embodiment of the present invention
• the term "concentric”, in relation to the concentric emitter tubes 14, means that the inner tube 14, is substantially centered in the outer tube 14 0 .
• evacuated means a vacuum such as is typically used for x-ray tubes.
• an x-ray tube 10 comprising an evacuated, electrically-insulative enclosure 11 with a cathode 13 and an anode 12 at opposite ends thereof.
• the enclosure 11 can be or can comprise a ceramic material.
• Dual, electrically-conductive emitter tubes 14 can extend from the cathode 13 towards the anode 12, and can comprise an inner tube 14, and an outer tube 14 0 .
• the inner tube 14, can be disposed at least partially inside of the outer tube 14 0 .
• the inner tube 14, and the outer tube 14 0 can have or share a common central region 8.
• the inner tube 14, and the outer tube 14 0 can be concentric.
• the inner tube 14, and the outer tube 14 0 can have a common longitudinal axis 17.
• some misalignment of the longitudinal axis 17 of the inner tube 14j with respect to the longitudinal axis 17 of the outer tube 14 0 may be preferred, such as for example for manufacturability considerations.
• the longitudinal axis 17 of the emitter tubes 14 can be substantially aligned with a longitudinal axis 6 of the enclosure 11. Alternatively, there can be some offset between a longitudinal axis 17 of the emitter tubes 14 and a longitudinal axis 6 of the enclosure 11. It can be beneficial to align the longitudinal axis 17 of both of the emitter tubes 14 with a longitudinal axis 6 of the enclosure 11 if x-ray emission from anode 12 center is desired.
• Each of the inner 14, and outer 14 0 tubes can have opposite ends (N and F) comprising a near end N associated with, disposed adjacent to, or attached to the cathode 13 and a far end F disposed closer to the anode 12.
• An electron emitter 18 can be coupled between a far end F, of the inner tube 14, and a far end F 0 of the outer tube 14 0 .
• the inner 14, and outer 14 0 tubes can be
• an electrically insulative material 9 can be disposed near or attached to the cathode 13 and can, along with the gap 7 (possibly a vacuum-filled gap), electrically insulate the inner tube 14, from the outer tube 14 0 .
• This electrically insulative material 9 can be an electrically insulative spacer ring and can partially fill a gap between the inner tube 14, and the outer tube 14 0 and can hold the inner tube 14, in proper position with respect to the outer tube 14 0 .
• the electron emitter 18 can be a filament.
• the filament can be various types or shapes including helical or planar.
• the far end F, of the inner tube 14 can include a radial projection 16 extending radially outwardly from the inner tube 14, towards the outer tube 14 0 .
• the radial projection 16 can extend towards a groove 15 in the far end F 0 of the outer tube 14 0 .
• Use of the radial projection 16 can allow the electron emitter 18 to be substantially centered across the far end F 0 of the outer tube 14 0 .
• a center 18 c of the electron emitter 18 can be substantially aligned with a longitudinal axis 6 of the enclosure 11, which can result in x-ray emission from a center of a transmission window on the anode 12.
• the far end F 0 of the outer tube 14 0 can substantially surround a circumference of the far end Fj of the inner tube 14, with the exception of the groove 15. This design can smooth out electric field gradients around the electron emitter 18 and the far end F of the emitter tubes 14.
• a length L, of the inner tube 14j can be greater than a length L 0 of the outer tube 14 0 .
• the near end N 0 of the outer tube 14 0 can terminate within the enclosure 11 and can contact an inner surface 13, of the cathode 13.
• the near end N, of the inner tube 14, can extend through the cathode 13 outside the enclosure 11.
• the inner tube 14j can initially remain open to allow the inner tube 14, to be a vacuum port to draw a vacuum on the inside of the x-ray tube. See for example, open inner tube 14, in FIG. 5 and vacuum pump 61 pumping out gases 62 in FIG. 6.
• the near end N, of the inner tube 14 can then be pinched shut, such as by crimping the tube walls together. This crimping or pinching can be done with a hydraulic tool operated at high pressure, such as greater than 500 psi. See for example pinching process and a tool 71 for pinching the inner tube 14, in FIG. 7.
• the near end N, of the inner tube 14, can then be defined as a pinched-shut end.
• Use of the inner tube 14, to act as a vacuum port can avoid the need of using a separate component for this function, thus saving
• the inner tube 14, can be made of or can comprise a soft or ductile metal that can be pinched shut, such as copper or nickel for example.
• the outer tube 14 0 can comprise titanium. Use of titanium can help in maintaining a vacuum inside of the enclosure 11 because titanium can absorb hydrogen. Due to the small size of the H 2 molecule, hydrogen can penetrate minute gaps in the x-ray tube, increase pressure therein, and cause the x-ray tube to malfunction. Thus, use of a titanium outer tube 14 0 can be beneficial for maintaining a desired level of vacuum in the x-ray tube and thus prolong the life of the x-ray tube.
• the outer tube 14 0 can comprise a mass percent of at least 85% titanium in one aspect, at least 95% titanium in another aspect, at least 99% titanium in another aspect, or at least 99.8% titanium in another aspect.
• a common feature of x-ray tube design is a cathode optic surrounding the electron emitter, to block electrons from extending radially outwards to the enclosure 11. These electrons can electrically charge the enclosure 11 and can result in early x-ray tube failure. With the x-ray tube design of the present invention, this optic can be avoided because the outer tube can substantially block electrons from extending radially outwards to the enclosure 11. By not using this cathode optic, manufacturing cost can be reduced. A cathode optic, however, may still be used with the present invention if needed for a highly focused electron beam.
• first gap Gi between the far end F 0 of the outer tube 14 0 and the anode 12 and a second gap G 2 between the far end F, of the inner tube 14i and the anode 12.
• the first gap Gi can be approximately equal to the second gap G 2 , thus keeping a plane of the electron emitter 18 substantially parallel to a face of the anode 12.
• a divergent x-ray emission it can be beneficial to dispose the electron emitter 18 near the anode 12.
• another benefit of disposing the electron emitter 18 closer to the anode 12 is that the electron emitter 18 can output the same power at a lower
• the dual, electrically-conductive emitter tubes 14 can provide a sturdy support for the electron emitter 18, even if the electron emitter 18 extends a substantial distance from the cathode 13 towards the anode 12.
• the first gap Gi can be smaller than a length L 0 of the outer tube 14 0 .
• the first gap Gi can be between 4% and 25% of a length of the outer tube 14 0 in one embodiment or between 7% and 15% of a length of the outer tube 14 0 in another embodiment.
• the electron emitter 18 can be disposed between 0.4 millimeters and 8 millimeters from the anode 12 in one embodiment or between 0.3 millimeters and 4 millimeters from the anode 12 in another embodiment.
• a power supply 41 can provide electrical power to an x-ray tube 48.
• the power supply 41 can include cathode electrical connections 45 and an anode electrical connection 46.
• the cathode electrical connections 45 can have a bias voltage that is several kilovolts
• the anode electrical connection 46 can be electrically connected to ground 47.
• the cathode electrical connections 45 can include a first cathode electrical connection 45 0 that is electrically coupled to the near end N 0 of the outer tube 14 0 and a second cathode electrical connection 45, that is electrically coupled to the near end Nj of the inner tube 14,.
• the power supply 41 can provide a small voltage differential, such as a few volts for example, between the first and second cathode electrical connections 45 to cause an electrical current to flow through the electron emitter 18 to heat the electron emitter 18.
• the heat of the electron emitter 18 and the large bias voltage between the electron emitter 18 and the anode 12 can cause electrons to emit from the electron emitter 18 towards the anode 12.
• a helical spring 42 can be used to provide electrical contact between the first cathode electrical connection 45 0 and the near end N 0 of the outer tube 14 0 .
• the helical spring 42 can be especially beneficial in a removable x-ray tube design because it can allow for easy electrical connection during x-ray tube insertion and removal and it can provide a large amount of electrical contact to the outer tube 14 0 .
• the electrical contact between the helical spring 42 and the outer tube 14 0 can be through a base plate of the cathode 13 if the outer tube 14 0 terminates within the enclosure 11.
• the pinched-shut near end N, of the inner tube 14 can be an electrical contact and can be configured to be electrically coupled to the power supply 41.
• the pinched-shut near end N, of the inner tube 14, can electrically contact the second cathode electrical connection 45, by various means, including by a hinge spring or a leaf spring 44.
• a leaf spring 44 can be convenient for providing electrical contact to the inner tube 14, in a removable x-ray tube design.
• a plunger pin or various other types of electrical connectors, can also be used for electrical connection between the cathode electrical connections 45 and the emitter tubes 14.
• the helical spring 42 and / or the leaf spring 44 can be substantially or totally enclosed within an electrically-conductive cup 43 that is capped off with the cathode 13.
• This cup can act as a corona guard to shield sharp edges of the helical spring 42, the leaf spring 44, and / or the emitter tubes 14.
• This corona guard can help to prevent arcing between these components and surrounding or near-by components having a large voltage differential.
• the emitter tubes 14, the cathode 13, and the electron emitter 18 can all be pre- assembled, then conveniently connected to the enclosure 11, thus allowing precise and repeatable placement of the electron emitter 18 in the x-ray tube during manufacturing, thus improving consistency of x-ray output between different units of a single x-ray tube model.
• a method, of evacuating and sealing an x-ray tube can comprise some or all of the following steps, which can be performed in the order specified:
• cathode 13 towards the anode 12 , and comprising an inner tube 14, disposed at least partially within an outer tube 14 0 ;
• the inner tube 14, and the outer tube 14 0 each having opposite ends comprising a near end N disposed adjacent to, associated with, or attached to the cathode 13 and a far end F disposed closer to the anode 12;
• an electron emitter 18 coupled between the far end F, of the inner tube 14, and the far end F 0 of the outer tube 14 0 ;
• the inner tube 14, and the outer tube 14 0 being electrically isolated from one another except for the electron emitter 18;
• the inner tube 14j being open with the near end N, of the inner tube 14, extending outside the enclosure 11 beyond the cathode 13; and vii. the enclosure 11 sealed off except for the open inner tube 14i;
• Sealing the x-ray tube 50 can be done by pinching the near end i of the inner tube 14, with a hydraulic tool operated at high pressure, such as greater than 500 psi, while the inner tube 14, is still connected to a vacuum.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• X-Ray Techniques (AREA)

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• 2014
  • 2014-07-08 US US14/325,896 patent/US9240303B2/en active Active
  • 2014-07-09 JP JP2016540880A patent/JP6311165B2/ja active Active
  • 2014-07-09 KR KR1020167006411A patent/KR102157921B1/ko active IP Right Grant
  • 2014-07-09 EP EP14844905.1A patent/EP3033761B1/de active Active
  • 2014-07-09 WO PCT/US2014/045987 patent/WO2015038229A2/en active Application Filing
  • 2014-07-09 CN CN201480049566.1A patent/CN105531791B/zh active Active

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